docs: def _load(self, filename=None):
          """Load the Himawari AHI RSR data for the band requested
          """
          if not filename:
              filename = self.filename
  
          wb_ = open_workbook(filename)
          self.rsr = {}
          sheet_names = []
          for sheet in wb_.sheets():
              if sheet.name in ['Title', ]:
                  continue
              ch_name = AHI_BAND_NAMES.get(
                  sheet.name.strip(), sheet.name.strip())
              sheet_names.append(sheet.name.strip())
              self.rsr[ch_name] = {'wavelength': None,
                                   'response': None}
              wvl = np.array(
                  sheet.col_values(0, start_rowx=5, end_rowx=5453))
              resp = np.array(
                  sheet.col_values(2, start_rowx=5, end_rowx=5453))
              self.rsr[ch_name]['wavelength'] = wvl
              self.rsr[ch_name]['response'] = resp